The Reference Optical Quartz sits at the top of QED’s three-tier optical cable range, above the Performance Optical Graphite and the entry-level Connect Optical. Where the lower tiers use PMMA acrylic glass fibre, the Reference Optical Quartz is built around QED’s Glasscore construction — 210 individual boro-silicate glass fibres, each measuring approximately 50 micrometres in diameter, bundled to form the 1mm core required by the Toslink standard.
Glasscore Construction
Boro-silicate glass has fundamentally different optical properties to PMMA acrylic. Each of the 210 glass fibres is coated with a cladding of low refractive index, which guides the light signal through a stepped refractive index profile. The smaller numerical aperture of glass fibre reduces the range of acceptance angles, channelling light along straighter paths within each fibre. In a multi-fibre bundle, light travels through many narrow, parallel channels rather than bouncing across the full diameter of a single large-core acrylic fibre — reducing modal dispersion and the timing errors that result from it.
Performance
The measurable advantages of the Glasscore approach are significant. Bandwidth exceeds 150MHz — comfortably beyond the demands of high-definition multi-channel digital audio — and remains unaffected by cable bending. Signal attenuation is less than 0.03 dB/m, approximately one-tenth the loss of traditional acrylic fibres. Jitter is typically 30 picoseconds, compared with up to 145ps from conventional acrylic optical cables. The cable supports 24-bit and 32-bit high-resolution audio, including 24-bit/192kHz.
By contrast, the Performance Optical Graphite below it in the range uses PMMA acrylic with attenuation of less than 0.15 dB/m — five times the loss per metre — and QED themselves recommend stepping up to the Reference Optical Quartz for HD multi-channel audio applications exceeding 12MHz bandwidth.
Applications
The Reference Optical Quartz connects any source component with a Toslink optical output — CD players, DACs, Blu-ray players, games consoles, televisions, and digital set-top boxes — to amplifiers, AV receivers, DACs, network music players, pre-amplifiers, and soundbars. The 2m length provides additional reach for connecting components across a wider equipment rack or between nearby furniture units.